66 lines
2.4 KiB
Bash
66 lines
2.4 KiB
Bash
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#!/bin/bash
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set -euo pipefail
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# Prints Zebra checkpoints, based on a list of block heights, sizes, ans hashes.
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#
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# Reads lines containing a block height, block byte size, and block header hash
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# from stdin. Writes each checkpoint to stdout, as a line with space-separated
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# fields.
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#
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# The block header hash is read in Bitcoin order, but written out in Zebra's
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# internal byte order.
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#
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# Usage: get-height-size-hash.sh | calculate-checkpoints.sh
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# get-height-size-hash.sh -testnet | calculate-checkpoints.sh
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#
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# calculate-checkpoints.sh ignores any command-line arguments.
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#
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# TODO: rewrite as a stand-alone Rust command-line tool.
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# zebra-consensus accepts an ordered list of checkpoints, starting with the
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# genesis block. Checkpoint heights can be chosen arbitrarily.
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# We limit the memory usage for each checkpoint, based on the cumulative size of
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# the serialized blocks in the chain. Deserialized blocks are larger, because
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# they contain pointers and non-compact integers. But they should be within a
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# constant factor of the serialized size.
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MAX_CHECKPOINT_BYTE_COUNT=$((256*1024*1024))
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# We limit the maximum number of blocks in each checkpoint. Each block uses a
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# constant amount of memory for the supporting data structures and futures.
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#
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# TODO: In the Rust implementation, set this gap to half the sync service's
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# LOOKAHEAD_LIMIT.
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MAX_CHECKPOINT_HEIGHT_GAP=2000
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cumulative_bytes=0
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height_gap=0
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while read -r height size hash; do
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cumulative_bytes=$((cumulative_bytes + size))
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height_gap=$((height_gap + 1))
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# Checkpoints can be slightly larger the maximum byte count. That's ok,
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# because the memory usage is only approximate. (This is a bash-specific
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# optimisation, to avoid keeping a copy of the previous height and hash.
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# Since exact sizes don't matter, we can use the same check in the Rust
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# implementation. Or choose a simpler alternative.)
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if [ "$height" -eq 0 ] || \
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[ "$cumulative_bytes" -ge "$MAX_CHECKPOINT_BYTE_COUNT" ] || \
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[ "$height_gap" -ge "$MAX_CHECKPOINT_HEIGHT_GAP" ]; then
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# Reverse the byte order of hash.
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#
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# We reverse the hash after selecting the checkpoints, because launching
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# a zebrad subprocess is expensive. (This is a bash-specific
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# optimisation, the Rust implementation should reverse hashes as it loads
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# them.)
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hash=$(zebrad revhex "$hash")
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echo "$height $hash"
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cumulative_bytes=0
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height_gap=0
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fi
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done
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